The subject of the invention is a sewing machine having a means for automatically severing the thread chain between successive pieces of sewing material, wherein:
(a) a cutting means is provided behind the sewing needle, in the feed direction of the sewing material, and laterally offset from the sewing axis;
(b) a suction means is associated with the cutting means for sucking the thread chain to the side and toward the cutting means;
(c) the feeder and the cooperating pressure plate of the presser foot of the sewing machine each have on their side more removed from the cutting means and the suction means a projection extending in the feed direction of the sewing material to an extent such that the cutting means and the ends of the feeder and of the pressure plate are substantially on one plane.
In known sewing machines equipped with a means for automatically severing the thread chain, each sewn piece of material, after its trailing edge has passed the end of the feeder and of the pressure plate of the presser foot, must be drawn forward to the cutting means. This makes the working surface of the sewing machine free for the next piece of sewing material. While the operator feeds a sewn piece to the cutting means by hand, he or she is prevented from continuing the sewing work proper.
The invention relieves the operator of the time-consuming handling activity described above. This results in a rise of productivity. The sewing machine is technically of very simple construction.
With the inventive sewing machine, each sewn piece of material is moved on without any help from the operator and without the use of any additional conveying means, and the thread chain between successive pieces of sewing material is automatically severed. When the trailing edge of a piece of sewing material has passed through about one third of the length of the feeder and the pressure plate, from the back edge of the latter, the operator can already concentrate on preparing the next piece of sewing material. The completion of the sewing process on the previous piece of sewing material and the passing on of the sewn piece take place automatically without the operator having to pay any special attention or intervene to pass on the sewn piece. It is also possible to convey the piece of sewing material automatically to further processing units after the thread chain has been severed.
The one-sided extensions of the feeder and the pressure plate cause the particular piece of sewing material to move obliquely forward laterally to the cutting means, slackening the thread chain between this piece and the following piece. This consequently facilitates the suction of the thread chain toward the cutting means.